The primary endpoint showed a non-significant relative risk
reduction of 17 percent in favor of clazosentan (p=0.1). The safety
profile of clazosentan in CONSCIOUS-2 was comparable to previous
studies with the compound in this disease.

Jean-Paul Clozel, M.D. and Chief Executive Officer of Actelion
commented: "These are, of course, disappointing results. Having
embarked upon such a complex study, both in terms of design and
execution, I must commend the exceptional efforts of all involved
delivering a high-quality study."

Jean-Paul Clozel continued: "Actelion will continue to focus on
growing its existing business. With four marketed products,
Actelion is generating the necessary revenues to continue to invest
appropriately in clinical studies for our more than 10 development
compounds."

In regards to the ongoing CONSCIOUS-3 study in patients with
aSAH that underwent coiling to secure their aneurysm, Actelion will
discuss the appropriate course of action with the Steering
Committee. The company will provide an update on the clazosentan
development program in its upcoming Q3 reporting, scheduled for
Thursday, 21 October 2010.

About CONSCIOUS-2

CONSCIOUS-2 (Clazosentan to Overcome Neurological iSChemia and
Infarct OccUrring after Subarachnoid hemorrhage) investigated the
potential clinical benefits of clazosentan through the primary
endpoint of vasospasm-related morbidity and all-cause mortality,
which includes neurological deterioration, new brain infarcts,
introduction of vasospasm rescue therapy, or death from any
cause.

CONSCIOUS-2 was a global study which concluded enrollment with
over 1,150 patients with aSAH and aneurysmal surgical clipping,
from more than 100 centers. Patients were randomized 2:1 to receive
either 5 mg/h of clazosentan, or placebo.

###

Notes to the Editor

About Cerebral vasospasm as a consequence of aneurysmal
subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening
condition affecting over 85,000 people in the EU, US and Japan
every year. This condition occurs when the rupture of an aneurysm
on the cerebral vessels leads to release of blood into the
subarachnoid space of the brain. Endovascular coiling or
microsurgical clipping is usually required to stop the bleeding and
prevent further episodes.

Cerebral vasospasm following SAH causes the intracranial
arteries to constrict thus diminishing blood flow to the brain. It
is a significant predictor of poor outcome and the leading
potentially treatable cause of mortality and morbidity in these
patients. Vasospasm is unpredictable in nature and seen in over 67%
of untreated patients with angiography at the time of maximum
spasm, around the end of the first week. It becomes symptomatic in
about half of these patients. Currently, there is no effective
treatment for the prevention and treatment of the severe
complications following vasospasm.

About CONSCIOUS-3

CONSCIOUS-3 is a Phase III study evaluating the efficacy and
safety of two doses (5 or 15 mg/h) of clazosentan versus placebo in
patients post-aSAH treated by endovascular coiling. The primary
endpoint is identical to that of CONSCIOUS 2. Until the end of
September 2010, the study enrolled close to 600 patients out of
1500 planned.

About CONSCIOUS-1

CONSCIOUS-1 was a multi-center, international, double-blind,
randomized, placebo-controlled, parallel-group, dose-finding study
to evaluate the efficacy of three dose levels of clazosentan (15, 5
and 1mg/hour) in preventing the occurrence of cerebral vasospasm
following aSAH in patients who underwent either clipping or coiling
to stop the initial bleed, assessed by angiography.

CONSCIOUS-1 showed a strong treatment effect on the primary
endpoint. Clazosentan significantly reduced moderate/severe
vasospasm at all tested doses, with a relative risk reduction
compared to placebo of 65% at the highest dose. A post-hoc analysis
showed a trend in favor of reducing morbidity/mortality related to
vasospasm using central assessment.

In the study, treatment with clazosentan was associated with
more adverse events than placebo, mainly related to vasodilatory
effects such as hypotension and fluid retention.

Actelion Ltd

Actelion Ltd is a biopharmaceutical company with its corporate
headquarters in Allschwil/Basel, Switzerland. Actelion's first drug
Tracleer®, an orally available dual endothelin receptor
antagonist, has been approved as a therapy for pulmonary arterial
hypertension. Actelion markets Tracleer® through its own
subsidiaries in key markets worldwide, including the United States,
the European Union, Japan, Canada, Australia and Switzerland.
Actelion, founded in late 1997, is a leading player in innovative
science related to the endothelium - the single layer of cells
separating every blood vessel from the blood stream. Actelion's
over 2,400 employees focus on the discovery, development and
marketing of innovative drugs for significant unmet medical needs.
Actelion shares are traded on the SIX Swiss Exchange (ticker
symbol: ATLN) as part of the Swiss blue-chip index SMI (Swiss
Market Index SMI®).

Drugs.com provides accurate and independent information on more than 24,000 prescription drugs, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment.